Johnson is a candidate to replace Ryan Weber in the starting rotation, Ian Browne of MLB.com reports.
Boston manager Ron Roenicke indicated that someone from the alternate training camp in Pawtucket would replace Weber, so Dylan Covey, who was called up Saturday after Weber was optioned, is expected to pitch out of the bullpen. "We already have plans on who's going to come up and be one of the other starters. And like we talked about, we're waiting to see if somebody takes off. And who knows? Maybe that will be the third or fourth spot and every fifth day we won't have to worry about it," Roenicke said. Johnson pitched a simulated game Friday, per Christopher Smith of MassLive.com, which puts the left-hander on schedule to throw Wednesday on regular rest. The Red Sox would need to add Johnson to the 40-man roster.